using System;
using System.Threading;

namespace Common
{
    public class CountDownLatch
    {
        private int remainingCount;
        private EventWaitHandle waitEventHandle;
        public EventWaitHandle WaitEventHandle => waitEventHandle;

        public CountDownLatch(int count)
        {
            Reset(count);
        }

        public void Reset(int count)
        {
            if (count < 0)
                throw new ArgumentOutOfRangeException();
            remainingCount = count;
            waitEventHandle = new ManualResetEvent(false);
            if (remainingCount == 0)
            {
                waitEventHandle.Set();
            }
        }

        public void Signal()
        {
            // The last thread to signal also sets the event.
            if (Interlocked.Decrement(ref remainingCount) == 0)
                waitEventHandle.Set();
        }

        public void Wait()
        {
            waitEventHandle.WaitOne();
        }
    }
}